Effects of Successive Applications of Preemergence Herbicides on Turf

Abstract

The effects of seven preemergence herbicides on turfgrass quality, clipping yield, root growth, thatch accumulation, and carbohydrate reserves of three turfgrasses were measured. Nearly all herbicides caused some effect on one or more of the turfgrasses at some point during the 8-yr experiment, especially during mid-summer stress periods. The most consistently injurious herbicide was bandane (polychlorodicyclopentadiene) which caused a marked reduction in turfgrass quality, poor rooting, and increased susceptibility to stripe smut (Ustilago striiformis West. Niesel.). Clipping yields were reduced only in red fescue (Festuca rubra L. ‘Pennlawn’) by bensulide [O,O-diisopropyl phosphorodithioate S-ester with N-(20mercaptoethyl)-benzenesulfonamide], siduron [1-(2-methylcyclohexyl)-3-phenylurea], and terbutol (2,6-di-tert-butyl-p-tolyl methylcarbamate). Except for bandane, only siduron and terbutol caused significant reductions in root growth, and only in ‘Kenblue’-type Kentucky bluegrass (Poa pratensis L.). Thatch accumulation was reduced in ‘Merion’ Kentucky bluegrass treated with benefin (N-butyl-N-ethyl-α,α,α,-trifluoro-2,6-dinitro-p-toluidine) in ‘Kenblue’-type Kentucky bluegrass treated with bandane, benefin, bensulide, and terbutol; and in ‘Pennlawn’ red fescue treated with bandane, calcium arsenate, and terbutol. Carbohydrate reserves were not significantly different among treatments.